The disclosure relates to a fuel injector, in particular a common rail injector, as disclosed herein.
A fuel injector as disclosed herein is known from EP 1 042 603 B1. The known fuel injector has within its injector housing a sensor which is arranged in the region of a return bore between a control chamber of the fuel injector and a low-pressure region. In particular, the sensor surrounds the return bore at a sleeve-like section of a component in which the return bore is formed. An end portion of an injection member configured as a nozzle needle projects into the control chamber. The movement of the nozzle needle is controlled in known fashion by influencing the pressure in the control chamber to open spray holes formed in the injector housing in order to inject fuel into the combustion chamber of an internal combustion engine. The pressure in the control chamber is effected by drainage of fuel from said control chamber into the low-pressure region via the return bore or return throttle, it being possible to close the return bore by means of a closing member in the low-pressure region of the injector housing, which closing member can in turn be actuated by means of an actuator, for example a magnetic actuator or a piezo actuator. In the lowered position of the nozzle needle a relatively high (hydraulic) pressure is present in the control chamber and therefore also in the return bore. Upon depressurization of the control chamber, by contrast, fuel flows from the control chamber into the low-pressure region, the hydraulic pressure in the return bore being reduced. The known sensor is designed to detect the pressure or pressure fluctuations in the return bore caused by opening of the closing member leading from the control chamber, from which the position of the nozzle needle can be deduced. A disadvantage of the known arrangement is that the sensor is arranged in the high-pressure region of the injector housing and must therefore be of relatively high-cost construction. In addition, the installation space available for such a sensor in the injector housing is restricted, so that special design solutions, which are critical, in particular, with respect to the strength of the injector housing, must be selected.
A fuel injector having pressure sensing means arranged in the low-pressure region is known from DE 10 2011 051 765 A1. In this case a measuring duct or tap hole leads to a diaphragm-like intermediate wall. The pressure sensing means or force sensing element is arranged on the rear side of the intermediate wall. The pressure sensing means is preferably a measuring strip arrangement of low stiffness, which measures the tensions or deformations arising in the intermediate wall. However, because of the high pressures in the tap hole, problems relating to the strength of the intermediate wall can arise.